Incendiary device



May 7 1957 N. J. THOMPSON INCENDIARY DEVICE Filed Nov` 14, 1944INCENDIARY DEVICE Norman J. Thompson, Wellesley, Mass., assignor vto theUnited States of America as represented by the Secretary of WarApplication November 14, 1944, Serial No. 563,352

1 Claim. (Cl. 102-6) The invention described herein may be manufacturedand used by or for the Government, for governmental purposes, withoutthe payment to me of any royalty thereon.

This invention relates to an incendiary device and a heater mixturetherefor, and more particularly to an incendiary device and heatermixture which are particularly adaptable for use in the construction ofan incendiary bomb.

One object of this invention is the provision of an incendiary devicewhich is unusually safe in storage and in transport.

Another object of this invention is .the provision of an incendiarydevice which is not subject to evaporation or leakage.

A further object of this invention isthe provision of an incendiarywhich is extremely diicult to extinguish with ordinary agents since itwill burn in the absence of oxygen from the surrounding atmosphere.

A still further object of this invention is the provision of anincendiary which is particularly effective since it combines the hightemperature and radiation characteristics of the common magnesium bomband the long reaching llames of the oil bomb.

A still further object of this invention is the provision of a heatermixture which is particularly adapted for use in the above indicatedincendiary.

lFurther and additional objects will appear from the followingdescription, the accompanying drawing and the appended claim.

In accordance with this invention, an incendiary device is providedwhich comprises preferably a fusible or combustible case (which may bereinforced with a strongnoncombustible case material such as steel), abody of substantially non-volatile combustible organic material of highcalorific value within said case and a second body of heater mixture,also within said case, capable of selfsustained burning at a reactiontemperature sufficient to melt or burn said case and to vaporize andcrack said organic material. Organic materials having suitable physicaland Vthermal properties are exemplified by fatty acids, fats, oils, andfatty esters, such as, stearic acid, oleic and tallow, and lard oil, buthydrocarbons and other mineralcarbonaceous materials which are readilyVavailable are preferred. The properties of high caloric value, highmelting point, and high boiling point are important factors in theselection of these materials. For obtaining proper cracking, the heatermixture should give a localized heat of adequate intensity but shouldnot burn too rapidly.

In accordance with one preferred embodiment of this invention, anon-volatile hydrocarbon mass is present in the form of a central coresurrounded by the heater mixture and the whole Iis containedin acombustible or fusible case provided with suitable means for ignitingthe heater mixture. The heater mixture, during burning, fuses or ignitesthe case and at the same time volatlizes and cracks the hydrocarbonmaterial to form vapors which nited States Patent are ignited. Thus thedevice possesses a high degree of effectiveness as an incendiary.

In accordance with one preferred embodiment of this invention, theheater mixture is placed in an annular space between the combustible orfusible case and the central hydrocarbon core. However, under certainconditions, it may be desired that the heater mixture be centrallylocated along the longitudinal axis of the device and surrounded by thenon-volatile hydrocarbon material.

The hydrocarbon core may comprise a heavy hydrocarbon oil disposedWithin an inner readily combustible receptacle, and to minimize thepossibility of leakage, the oil may be practically solidified. This hasbeen done effectively by providing a hydrocarbon-containing masscomprising cotton waste saturated with a heavy hydrocarbon oil and alsoby converting a heavy hydrocarbon oil to a solid mass by the use ofsuitable emulsifying agents. If desired, the hydrocarbon material may bea solid resinous or wax-like mass. In this event a separate receptaclewill not be required for it.

The heater mixture for the device of this invention mayV with standardheater mixtures such as thermite or ther-v mate. Such a mixturecomprises a heavy hydrocarbon oil, fine ake aluminum and sodium nitrateto which nely divided sulphur may be added to insure evenness ofburning. The ingredients of the mixture may be proportioned to controlthe rate of burning and the total amount of heat liberated. The surfaceof the line flake aluminum permits the adsorption of large proportionsof the hydrocarbon oil (having a high caloric value) without destroyingthe burning properties of the mixture. The larger proportion of oil atthe same time provides a mixture insensitive to impact.

For a more complete understanding of this invention, reference is nowmade to the accompanying drawing wherein:

Fig. 1 is a broken sectional elevational View of an incendiary deviceconstructed in accordance with one embodiment of this invention;

Fig. 2 is a fragmentary sectional view of the device shown in Fig. ltaken along the line 2 2 thereof;

Fig. 3 is a broken sectional elevational View of a modified form of theincendiary device; and

Fig. 4 is a fragmentary sectional view of the device shown in Fig. 3taken along the line 4 4 thereof.

Referring now more particularly to Fig. 1, the device there showncomprises an outer case 10 which may be constructed of a fusible orcombustible material such as magnesium, aluminum, paper, nitrocelluloseor other similar substance. This case is secured by suitable means to abase 12. A second case 14 is disposed within and spaced from the sidewalls of case 10. The case 14 is constructed of a readily combustiblematerial such as paper, nitrocellulose or other readily combustibleplastic. A non-volatile hydrocarbon core 15 is positioned within theinner case i4. This mass of material may comprise cellulose cotton wastesaturated with a heavy hydrocarbon oil. However, it Will be apparentthat the heavy hydrocarbon may be present in other physical forms ifdesired. The hydrocarbon material may be a solid, self-supportingwax-like or resinous mass, in which case the inner receptacle 14 may bedispensed with. One advantage of such a construction is that the deviceis more readily-assembled Gilsonite or other hydrocarbon resin,

wax, or emulsion has been found to be useful for this purpose. `Onesolid emulsion that has been found to be satisfactory for this purposewas prepared by cooking 87% by weight of #2 fuel oil and- 13% by weight,of aluminum soaps of cocoanut-fatty 4acids together` for about 30minutes at 212 F.

In the annular space between the side walls of the case and the case 14is provided a heater mixture 16 which is capable of self-sustainedburning and which will liberate sufficient heat to burn or fuse thecombustible case 10 and to Volatilize and crack the hydrocarbon core.The heater mixture may comprise thermite, which is a mixture of ironoxide and aluminum powder in the ratio of about 3 to 1. Otherthermite-like mixtures, such as thermate, may also be employed.A-typical thermate composition comprises 80% thermite and ,20% of a aremixture comprising:

Percent Barium nitrate 75 Aluminum flake 19 Sulphur 4.5 Castor oil 1.5

However, in accordance with one embodiment of this invention, amixturercomprising suitable proportions of heavy hydrocarbon oil, tineake aluminum and sodium nitrate may be used as the heater mixture. Ithas been found that the use of tine ake aluminum in mixtures of thischaracter imparts properties to the resulting mixture that have beenheretofore unobtainable. The tremendous surface area of the flakedaluminum will absorb a large amount of the heavy hydrocarbon oil (havinga high caloric value) and will thus permit relatively large amounts ofoil in the mixture without interfering with the burning characteristics.Moreover, the mixture is insensitive to impact when a larger proportionof hydrocarbon oil is used. Sulphur may be added to the mixture toinsure evenness of burning if desired. A suitable mixture has been foundto have the following composition:

Percent Motor oil (SAE-40) 15 Aluminum ake (through 200 M.) 35 Sulphur(through 100 M.) 2 Sodium nitrate (through 100 M.) 48

The relative proportions of the above indicated ingredients may bevaried depending upon the desired burning rate and total heat output.This in turn may depend upon the characteristics of the fusible orcombustible case. Lesser amounts of oil increases the burning rate anddecreases the total heat output and vice versa. Also thermite orthermate may be incorporated into the above indicated mixture in orderto control the burning properties thereof. Higher percentages ofthermite or thermate tend to increase the local heat produced. In'theevent that the fusible or combustible outer case 10 comprises magnesiumthen a suitable mixture has been found to be 50% standard thermate and50% of the above indicated composition. In the event that nitrocelluloseor other readily combustible material is used in the construction of thecase 10, then the heater mixture may comprise smaller proportions ofthermite or thermate and higher percentages of oil may be used.

In a completed form of the bomb the top of the case 10 may be providedwith a suitable cover 17 and means for igniting the heater mixture. Suchigniter means may comprise black powder whose burning may be initiatedby a suitable firing mechanism.

Although the general design of the body, the closure, and fuze in thedevice may be varied, the drawing illustrates forms of bomb bodiesprovided with a standardized tail cup closure assembly and astandardized all-ways fuze assembly. The tail cup closure 17 is given apress t into a tail end extension of the bomb body and is l chromate.

crimped to the edge of this extension to make the tail cup more securein place, also, to which it may be welded. The all-ways fuze is securedat its head plug 18 to an apertured hub 19 disposed centrally in thebottom of the tail cup 17 so that a iirst fire charge 20 at the base ofthe fuze assembly is surrounded by the heater mixture 16. Arming of thefuze is subject to a release band 21, which held in place as shownprevents the fuze from being armed so long as an adjacent bomb in acluster holds theV band 21 in place. TheY tail cup hub 19 is encircledby a retaining ring 22 which may be used to secure the ends of clothstreamers (not shown) for stabilizing the bomb and regulating its speedin ight. Ring 22 also holds clip 23 in place as a catch forband 21.

The all-ways fuze assembly comprises a tubular fuze body 24 secured tohead plug 18 and a base plug 25, with which the body 18 forms a hollowchamber having conical end surfaces. The ring mechanism inclosed in thishollow chamber is made up of a striker body 26 slidably coupled with aprimer holder 27 and kept normally separated from a primer cap 28 in theprimer holder by a safety pin 29 and by a coil spring 30. An larming pin31 is passed through a central bore in the head plug 18 so that itprojects into the striker 26, wherein the arming pin positions thesafety pin 29 outwardly against a small coil spring 32 surrounding thesafety pin to thereby lock Y the striker against movement. Ejection ofthe arming pin from the head plug 18 by spring 33, when the release band21 no longer presses on the head of the arming pin, allows the safetypin 29 to become recessed within the striker 26 by the coil .spring 32so that the coupled striker and primer holder are no longer fixed inposition, and the striker-26 is free to move against coil spring 30 inthe direction of a primer cap 28 within the primer holder 27. Thetiringrmechanism assembly thus armed is free to gyrate in the hollowchamber with the outer ends of the striker and the primer holder slidingon the cam-like conical end surfaces of the chamber. When the tiringmechanism assembly is free to make such a movement, the striker 26 andprimer holder 27 are forced together and upon impact of the bombcarrying the fuze, with sufficient set-back force, the striker 26overcomes the resistance of coil spring 30 to drive tiring pin 41 intoprimer cap 28 seated in the primer holder 27. The armed firing mechanismis capable of functioning Vregardless of the position of the bomb onimpact. The primer cap 28 is seated above a bore 34 extending through aprimer holder 27. A flash back from the tired primer cap 28 passesthrough thisr bore and throughan aperture 40 in base plug 25 to ignite atirst tire charge 20 attached to the base plug 25 by a combustibleplastic cup 35.

A cotter pin36 through aligned drill holes in the head plug 18 and thehead of the arming-pin 31 maintains the fuze unarmed until it isassembled to the bomb with the release band 21 in place on the clusteredbomb. Spring band 37 is riveted to band 21 to assist in holding it inplace. v

After a bomb cluster is dropped from air craft, the release band 21unhinges from a bomb separated from the cluster and thereupon the armingpin 31 is ejected from the fuze to arm the tiring mechanism. When thebomb carrying the armed fuze receives adequate impact on hitting atarget, the primer becomes ignited by percussion and tiashes back intothe tirstptiring charge. lf desired a powder train delay element may beinserted into the bore 34 of the primer holder 27 Vor into the aperture40 of the fuze base plug 25.

A suitable first tire charge which does not burn explosively comprises25% magnesium and 75% barium To vent gases from the bomb when the heatermixture begins to burn, a smallrvent hole may be made in the upper partofthe bomb body and a small blowout plug may be normally fitted in thishole.V *In* operation, theheater mixture burns downwardly from the upperregions of the case 10 causing the case to fuse or burn as the mixtureburns down. When the mixture has burned down as far as the hydrocarboncore, the latter is caused to vaporize and the hydrocarbon is cracked.The cracked vapors are ignited and a very intense burning is produced.The incendiary is almost impossible to extingui-sh by ordinary agentsbecause of the presence of oxidizing agents (iron oxide and NaNOa) inthe heater mixture which provide the necessary oxygen for combustion.

A modified form of the incendiary device is shown in Figs. 3 and 4. Thismodified form comprises a hydrocarbon core 1S and a heater mixture 16similar to the device shown in Figs. 1 and 2. The outer case, however,comprises a layer of nitrocellulose reinforced with a perforated steelsleeve 39. This sleeve serves to reinforce the case so that the devicewhen used as a bomb will not be deformed on impact. Other noncombustiblereinforcing agents such as expanded metal, Wire screen, or otherforaminous sheet material may be employed if desired. However, the useof a perforated steel sleeve is preferred for the reason that, as thecontents of th-e case are being bur-ned, jets of llame Will be projectedthrough the perforations thus setting fire to any combustible objectthat happens to be positioned near the burning incendiary. In actualproduction the nitrocellulose layer may be molded directly inside of andinto the perforated steel case whereby the perfor-ations ane lled withthe nitrocellulose.

It will thus be seen that an incendiary device has been disclosed hereinwhich may be readily and cheaply prepared. By having its charge in asubstantially solid and non-volatile condition, the device is notsubject to evaporation or leakage, during storage or handling, yet whenfunctioning, gives lthe effects of long aming jets of gas. It is diicultto extinguish and the mixture contained therein is not sensitive toimpact, thus rendering lthe dcvice safe to transport. The ingredients ofthe heater mixture may be proportioned to provide any desired burningrate and heat liberation that may be required for effectiveness againstany Igiven target.

While in the foregoing several specific embodiments of this inventionhave been specifically disclosed it is not intended that the inventionshould be limited strictly thereto. It will be apparent to one skilledin the art that many modifications may be made and it is thereforeintended that this invention be limited only by the scope of theappended claim.

I claim:

An incendiary bomb including means for cracking oil within said bomb andbeing charged with heavy lhydrocarbon oil adapted to be cracked by saidmeans in said bomb, said means comprising a bomb casing having anitrocellulose wall portion and a surrounding, reinforcing steel sleeveprovided with a plurality of perforated portions through which jets ofarne are outwardly and forcibly directed through said sleeve forigniting combustibles in the vicinity of said bomb, said casingcontaining an inner core of cotton impregnated with heavy hydrocarbonoil, a beater composition in which said core is imbedded and held apartfrom said wall portion consisting essentially of an admixture of avolatile hydrocarbon oil, ther-mite, and a are mixture, said tiaremixture consisting by weight of from about 19% to about 35% of linealuminum flakes providing, in aggregate, a surface area highly adaptedto absorb a large quantity of heavy hydrocarbon oil, 4from about 48% to75% of fine particles of a readily oxidizable nitrate selected from thegroup of nitrates consisting of sodium nitrate and barium nitrate andfrom about 1% to about 2% of sulfur in the form of line particlesadapted to make said composition burn more evenly.

References Cited in the le of this patent UNITED STATES PATENTS1,174,925 Arndt Mar. 7, 1916 1,306,747 Chanard June 17, 1919 1,313,068Chanard Aug. 12, 1919 1,484,190 Ray Feb. 19, 1924 1,877,232 Duncan Sept.13, 1932 2,035,509 Schladt Mar. 31, 1936 2,318,994 Helmbold May 11, 19432,445,311 Cook et al July 20, 1948 FOREIGN PATENTS 17,788 Great Britainof 1908 449,193 Great Britain June 22, 1936 453,795 Great Britain Sept.18, 1936 OTHER REFERENCES Colliers Magazine (article: Wing Talk), March8, 1940 (page 6).

